With continuous improvement in recording capacity of an optical disk drive for recording, a variety of products such as conventional CD using the infrared laser (wavelength: 780 nm), DVD using the red-color laser (wavelength: 650 nm), Blu-ray disk (BD) and High Density (HD)-DVD using blue-color laser (450 nm) have been put into the market.
For example, the write strategy technology (refer to write strategy illustrated in FIG. 5) used for the DVD-RAM utilizes a plurality of laser pulses having three kinds of power level. Three kinds of power level can be sequentially classified, from the higher level, into the write power (Pw), gap power (Pg), and erase power (Pe). When an optical disk is irradiated with the laser beam of write power, recording film of the optical disk is fused. Thereafter, when the optical disk is cooled rapidly, the optical disk gets the amorphous (non-crystal) state and its light reflectivity is lowered. Such lowered reflectivity is utilized as a recording mark. Moreover, when the optical disk is irradiated with the laser beam of erase power, the recording film of optical disk gets the crystal state. A part of the optical disk in the amorphous state before irradiation of laser beam gets the crystal state and a part of the optical disk which has been initially in the crystal state is left as the crystal state. Therefore, the recording mark can be erased.
The recording strategy includes a rectangular mono-pulse employed in the CD-R, DVD-R (refer to FIG. 8), a comb type multi-pulse employed in the CD-RW, DVD-RW, DVD-RAM (refer to FIG. 5) and castle type (non-multi type) recording pulse employed for high multiple speed recording of optical disk of the DVD system (refer to FIG. 6).
The values for determining edge timing of the write strategy illustrated in FIGS. 5, 6, and 8 and the values (for example, Pw, Pg, Pe) for determining recording powers such as Pw and Pe are called write parameters. These write parameters are previously recorded as the optimum values for each recording medium. For example, in the case of DVD-RAM, these parameters are recorded in the physical format information (PFI) area within the control data zone provided in the lead in area at the inner circumference. The reason is that the optimum value of the recording parameter group is different in accordance with composition and material or the like of a recording medium.
Namely, on the occasion of recording the recording marks, the optimum recording marks are formed by reading the write parameters such as a value for determining edge timing of the write strategy, a value for determining recording power like Pw, Pm, and each value of shift table from the recording medium and then controlling the laser pulse using the write parameters obtained.
The write strategy technology explained above is described in the Japanese Unexamined Patent Publication No. 2003-85753 (corresponding USP No. 2003-67857).
On the other hand, a rotation control system for recording and reproducing operations of an optical disk can roughly be classified into two kinds of system. One system Is a CLV (Constant Linear Velocity) system for controlling the rotation of disk into a constant linear velocity and the other system is a CAV (Constant Angular Velocity) system for controlling the rotation of disk into a constant angular velocity.
In the CLV system, when the linear velocity at the outer and inner circumferences of a disk in the diameter of 120 mm is set identical, the number of rotations at the inner circumference changes to about 2.5 times the velocity at the outer circumference. Therefore, the rotating velocity determined in accordance with the linear velocity at the inner circumference is considered as a bottle-neck for realization of high speed recording and reproducing operations through improvement in the linear velocity. But, in the CAV system, high speed operations can be realized easily using the linear velocity at the outermost circumference because the number of rotations is constant. However, in the CAV system, since the number of rotations is constant, the linear velocity at the inner circumference changes about 2.5 times the velocity at the outer circumference and the recording velocity also changes about 2.5 times. Accordingly, the recording parameter group is also different in the inner circumference and outer circumference. In addition, since the linear velocity changes from time to time toward the outer circumference from the inner circumference, it is required to change the write parameters from time to time in accordance with change in the radial locations. For example, in the case of DVD-RAM of 5 times velocity, the recording parameter groups in the 2 times, 3 times, and 4 times velocity are provided from a medium manufacturer. Meanwhile, in the case of conducting the recording operation with the CAV system of 2 times velocity at the inner circumference and 5 times velocity at the outer circumference using a certain drive, the optimum recording parameter group of such drive is determined for 2 times velocity at the inner circumference and 5 times velocity at the outer circumference, while the recording quality is verified, on the basis of the recording parameter group provided from the medium manufacturer (this process is described hereinafter as learning of the recording parameter) and recording operation is executed while drive individually obtains the write parameters for the intermediate velocity. In this case, however, interpolation is conducted in general between the highest velocity and lowest velocity. The technology explained above is described in the Japanese Unexamined Patent Publication No. 2004-234699 (corresponding USP No. 2004-145993).